Organochlorine Compounds and Trace Elements in Fish Tissue and Streambed Sediment
in the Mobile River Basin, Alabama, Mississippi, and Georgia, 1998

U.S. Geological Survey
Water-Resources Investigations Report 02-4160

Abstract

During the summer of 1998, as part of the National Water-Quality Assessment
Program, a survey was conducted to determine which organochlorine compounds
and trace elements occur in fish tissues and streambed sediments in the Mobile
River Basin, which includes parts of Alabama, Mississippi, Georgia, and Tennessee.
The data collected were compared to guidelines related to wildlife, land use,
and to 1991 and 1994 National Water-Quality Assessment Program Study-Unit data.

Twenty-one sites were sampled in subbasins of the Mobile River Basin. The subbasins
ranged in size from about 9 to 22,000 square miles and were dominated by either
a single land use or a combination of land uses. The major land-use categories
were urban, agriculture, and forest.

Organochlorine compounds were widespread spatially in the Mobile River Basin.
At least one organochlorine compound was reported at the majority of sampling
sites (84 percent) and in a majority of whole-fish (80 percent) and streambed-sediment
(52 percent) samples. Multiple organochlorine compounds were reported at 75
percent of the sites where fish tissues were collected and were reported at
many of the streambed-sediment sampling sites (45 percent). The majority of
concentrations reported, however, were less than 5 micrograms per kilogram in
fish-tissue samples and less than 1 microgram per kilogram in streambed-sediment
samples.

The majority of trace elements analyzed in fish-liver tissue (86 percent) and
streambed-sediment (98 percent) samples were reported during this study. Multiple
trace elements were reported in all samples and at all sites.

Based on comparisons of concentrations of organochlorine compounds and trace
elements in fish-tissue and streambed-sediment samples in relation to National
Academy of Science and National Academy of Engineering and Canadian tissue guidelines,
probable-effects concentrations, and mean probable-effects concentration quotients
for streambed sediment, the potential exists for adverse effects to wildlife
at 15 (72 percent) of the sites sampled. The potential for adverse effects at
these sites is because of the presence of residues or breakdown products related
to polychlorinated biphenyls (PCBs), chlordane, dichlorodiphenyltrichloroethane
(DDT), chromium, lead, and zinc.

The majority of compounds reported (65 percent) were chlordane, DDT, and PCBs,
or their breakdown products. Concentrations of chlordane and heptachlor epoxide
in whole-fish tissue were positively correlated to the amount of urban land
use in a basin. Total DDT concentrations in whole-fish tissues were positively
correlated to agriculture.

The relation of trace elements to land use is not as clear as the relation
of organochlorine compounds to land use. This lack of clarity may be due to
the possibility of geologic sources of trace elements in the Mobile River Basin
and to the ubiquitous nature of many of these trace elements. However, there
may be a correlation between the amount of urban land use and concentrations
of antimony, cadmium, lead, and zinc in streambed-sediment samples from the
Mobile River Basin.

Fewer organochlorine compounds and trace elements were reported in samples
from the Mobile River Basin than in samples collected during the 1991 and 1994
National Water-Quality Assessment Program studies. Of the organochlorine compounds
analyzed nationally, 57 percent were reported in whole-fish tissue samples collected
locally and 41 percent were reported in streambed-sediment samples collected
locally, whereas 96 percent and 86 percent, respectively, were reported nationally.
Of trace elements analyzed nationally, 86 percent were reported in fish-liver
tissue locally and 95 percent were reported in streambed-sediment samples locally,
whereas 95 percent and 98 percent, respectively, were reported nationally.

In general, concentrations of organochlorine compounds and trace elements and
the frequency with which they were reported in the Mobile River Basin are similar
to or less than those reported by 1991 and 1994 Study Units; however, exceptions
do exist to this generality.

Exceptions are the higher reporting frequency of heptachlor epoxide, p,p'-DDT,
and PCBs in whole-fish samples, higher quartile concentrations of heptachlor
epoxide and p,p'-DDT in whole-fish samples, the higher maximum concentration
of heptachlor epoxide in whole-fish samples, and the higher maximum concentration
and reporting frequency of trans-chlordane in streambed-sediment samples in
the Mobile River Basin. In addition, aluminum, barium, chromium, cobalt, nickel,
and strontium were reported more frequently in fish-liver samples locally than
nationally, boron concentrations were consistently higher in fish-liver samples
locally than nationally, and mercury, silver, and ytterbium were reported more
frequently in streambed-sediment samples from the Mobile River Basin than nationally.

The higher reporting frequencies and concentrations of heptachlor epoxide,
p,p'-DDT, and trans-chlordane in samples from the Mobile River Basin are probably
due to the greater use of these compounds locally than nationally. The reason
for the higher reporting frequency of PCBs is less clear, but may be due
to the production of these compounds within the basin.

The higher frequency with which some trace elements were reported in fish-liver
tissue and streambed-sediment samples in the Mobile River Basin may be due to
geology or anthropomorphic activities. Higher boron concentrations locally are
probably due to anthropomorphic activities, because there are no major geological
sources for boron in the Mobile River Basin. Potential sources locally for most
of these trace elements include irrigation drain water (mercury), coal combustion
(mercury and nickel), metallurgy (barium, boron, chromium, and nickel), soaps
(boron), and the wood and pulp industry (barium and chromium). Other sources
that could enrich samples from the Mobile River Basin are the Black Warrior
coal fields (aluminum and mercury) in the northwestern quarter of the basin,
which are known to have elevated levels of mercury, and barite deposits (barium)
in east-central Alabama.

CONTENTS

Abstract

Introduction

Purpose and scope

Description of the Mobile River Basin

Study design

Acknowledgments

Methods of data collection and analysis

Sample collection and laboratory analysis

Quality assurance and quality control

Data analysis

Organochlorine compounds and trace elements

Fish-tissue samples

Comparison of concentrations of organochlorine compounds and
trace elements in
whole-fish tissue samples to standards and guidelines

Relation of organochlorine compounds and trace elements in
whole-fish tissue samples
to land use

Comparison of concentrations of organochlorine compounds and
trace elements in
fish-tissue samples to 1991 and 1994 National Water-Quality Assessment
Study-Unit data

Streambed-sediment samples

Comparison of concentrations of organochlorine compounds and
trace elements in
streambed-sediment samples to standards and guidelines

Relation of organochlorine compounds and trace elements in
streambed-sediment samples to land use

Comparison of concentrations of organochlorine compounds and
trace elements in
streambed-sediment samples to 1991 and 1994 National Water-Quality
Assessment Study-Unit data

Comparison between sampling media

Summary and conclusions

References cited

Appendixes

The text and graphics are presented here in pdf format (print
quality):